Most of the MCUs use (transistor-transistor logic) TTL levels, and our computer serial COM port generally uses RS232 serial logic level, to get the computer to communicate with the MCU, this RS-232 To TTL Converter can help you convert RS232 into 5V TTL and obtain quick and reliable signal conversion. It has a db-9 female connector on the RS232 serial end, and db-9 male connector on the TTL end. A separate terminal block is included. The terminal blocks plugs into the TTL port, providing screw-lug wire terminations for the port. A small-footprint serial RS232 level shifter breakout tool and no software or drives required, it is suitable for most applications e.g. in factories where TTL signals are used in micro-controller and embedded electronic equipment; to connect with device that only communicates using TTL signals, from your source RS232 device; to monitor and control industrial and automotive sensors and devices. Specific 9 pin D-Sub DB9 female port 3 pin connector - GND, Logic out (TX), Logic In (RX) Suitable for use with most micro-controllers Baud rate: 300bps to 115.2Kbps Full Duplex Support It’s port powered from RS-232 signal, no external power required Automatic send / receive data, without external flow control signals. Zero delay automatic transmission What’s Included 1 x Female RS232 DB9 to DB9 Male TTL Converter 1 x Female RS232 to 3 pinTerminal Board (RXD TXD GND) 1 x User Manual Noted: If your host device doesn't feature a native RS232 port, the versatile converter can be coupled with a USB to RS232 serial adapter (ASIN:B00H8HDS2K ).